This invention relates to an automatic conveyance system for automatically conveying cargo such as machine or electrical parts for assembly, raw materials, partially fabricated products and the like between a plurality of places in an assembling, processing or production plant, factory or the like, in which assembling, processing or production apparatus are disposed.
Automation has been advanced in production lines connecting a number of production areas with many assembling, processing or production apparatus (hereinafter referred to simply as production apparatus) installed therein for conveying cargo such as raw materials, parts, partially finished products and the like among the apparatus. In general, a production line includes a plurality of production areas, and one or more production apparatus are installed in each production area.
FIG. 7 is a schematic plan view outlining a prior art conveying system. This prior art conveying system includes a plurality of production areas in which various production apparatus 101 are installed, a plurality of production area conveying systems 105 one for each production area for conveying cargo such as parts, partially finished products, etc., within each production area, and also a main or inter-area conveying system 107 for conveying cargo among the plurality of production areas. Each production area conveying system 105 includes a production, area track 109 installed on its floor connecting the production apparatus 101 installed within each production area, a production area conveying vehicle 111 which runs along the production area track 109 for conveying cargo to be used for production, and a cargo transfer unit 113 at one end of the production area track 109 for transferring cargo between the production area conveying system 105 and the main conveying system 107. The main conveying system 107 includes a straight or rectilinear main track 115 which is provided to connect all the production areas 105 and which is used mainly when there is a long distance between a source area and a destination area where respective production apparatus 101 are present, a main conveying vehicle 117 which runs along the main track 118, a plurality of auxiliary tracks 118 which are provided near and in parallel with the main track 115 so as to connect a plurality of production areas 105 comparatively close to one another and which are used mainly when there is a short distance between a source area and a destination area where respective production apparatus 101 are present, and auxiliary conveying vehicles 119 which run along the auxiliary tracks 118.
A sequence of conveyance will now be described in connection with the case when cargo such as parts, partially fabricated products, etc., is conveyed from a production apparatus 101-1 in one production area 105 (e.g., a bottom left one in FIG. 7) a different production apparatus 101-2 in another production area 105 (e.g., a top right one in FIG. 7) relatively distant therefrom.
In the source production area, the cargo is loaded on the production area conveying vehicle 111-1 from a production apparatus 101-1 this area and then conveyed by the conveying vehicle 111-1 along a track 109-1 to a cargo transfer unit 113-1 at one end the track. At the cargo transfer unit 113-1, the cargo is transferred to an auxiliary conveying vehicle 119 of a nearby production area conveying system 107 and conveyed to the neighborhood of a nearby cargo transfer unit 115-1 on the main track 115 for transfer no the main conveying vehicle 117. Then, the main conveying vehicle 117 is moved along the main track 115 to the nearest cargo transfer unit 115-2 on the main track 115 to the destination production area, in which a destination production apparatus 101-2 is present. At the cargo transfer unit 115-2, the cargo is transferred to an auxiliary conveying vehicle 119 and then conveyed to the neighborhood of a cargo transfer unit 113-2 at one end of the track 109-2 in the destination production area. In this cargo transfer unit 113-2, the cargo is transferred to the production area conveying vehicle 111-9, and conveyed along the track 109-2 to the destination production apparatus 101-2.
In the production line provided with a plurality of such conveying systems 105 and 107, the cargo used for the production, when conveyed between two distant production areas, is subject to loading and unloading operations not only at the source and destination production apparatus 101-1 and 101-2 but also at a plurality of intermediate cargo transfer units 113-1, 115-1, 115-2 and 113-2.
Thus, with the above-mentioned prior art conveying system, when cargo is conveyed between two distant production areas, it is conveyed by a plurality of conveying vehicles 111-1, 119, 117, 119, and 111-2 from the source production apparatus 101-1 to the destination production apparatus 101-2. Therefore, many loading and unloading operations are required at a plurality of cargo transfer units 113-1, 115-1, 115-2 and 113-2, i.e., between the production area conveying vehicle 111-1 in the source area and an auxiliary conveying vehicle 119 near this area, between this vehicle 119 and the main conveying vehicle 117, between this vehicle 117 and an auxiliary conveying vehicle near the destination area, and between this vehicle 119 and the production area conveying vehicle 111 in the destination area. In addition, depending on the traffic situations of the individual conveying vehicles, it is necessary to wait for transfer between vehicles. Due to such loading and unloading operations as well as waiting times, a long time is required for the entire conveyance. Further, when it becomes necessary for the cargo to wait for vehicle transfer, the cargo has to be tentatively stocked for a while at each transfer site. This requires stockers and stocking or storage spaces, thus increasing the necessary equipment in the factory, which Is undesirable from the standpoint of effective space utilization within the factory premises.